Bondhead lead clamp apparatus

ABSTRACT

An apparatus and method of forming improved wire bonds between the contact pads on semiconductor devices and individual lead frame fingers of a lead frame. The present invention includes the use of an individual independent lead finger clamp during the wire bonding process to provide increased stability of the individual lead finger for improved bonding. If desired, the present invention also provides for the use of a conventional fixed clamp for the lead fingers during the wire bonding process in addition to the individual independent lead finger clamp during the wire bonding process to provide increased stability of the individual lead finger for improved bonding. The present invention also contemplates the replacement of the fixed clamp with another, or second, independent clamp in addition to the first individual independent lead finger clamp during the wire bonding process.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/955,561, filed Sep. 18, 2001, pending, which is a continuation ofapplication Ser. No. 09/337,782, filed Jun. 22, 1999, now U.S. Pat. No.6,290,116, issued Sep. 18, 2001, which is a divisional of applicationSer. No. 08/865,911, filed May 30, 1997, now U.S. Pat. No. 6,000,599,issued Dec. 14, 1999, which is a continuation of application Ser. No.08/597,616, filed Feb. 6, 1996, now U.S. Pat. No. 5,647,528, issued Jul.15, 1997.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is related to forming wire bonds betweenthe contact pads on semiconductor devices and individual lead framefingers of a lead frame.

[0004] More specifically, the present invention is related to theapparatus and method of forming improved wire bonds between the contactpads on semiconductor devices and individual lead frame fingers of alead frame using one or more independently actuated bondhead lead clampsduring the bonding process.

[0005] 2. State of the Art

[0006] Well known types of semiconductor chip devices are connected to acomponent known as lead frames and subsequently encapsulated in plasticfor use in a wide variety of applications. The lead frame is typicallyformed from a single continuous sheet of metal, typically by metalstamping operations. The lead frame includes an outer supporting frame,a central semiconductor chip supporting pad and a plurality of leadfingers, each lead finger having, in turn, a terminal bonding portionnear the central chip supporting pad. Ultimately, the outer supportingframe of the lead frame is removed after the wire bonds between thecontact pads of the semiconductor chip device and the lead fingers aremade.

[0007] Since the lead frames are formed continuously using stampingoperations, they are typically continuously rolled on a suitable reeland provided for use. Such reeling operations of the lead frames causethe lead frames to have induced deformations therein leading to leadframes exhibiting longitudinal curvature and transverse curvature. Suchlead frame curvature and any attendant deformation of the lead framecause problems in the formation of reliable wire bonds with the contactpads of semiconductor devices and the individual lead fingers of thelead frame, particularly, when the size of the semiconductor isdecreased, the number of contacts pads on the semiconductor device isincreased, and the number of lead fingers on the lead frame isincreased.

[0008] Typical apparatus and methods for forming the wire bonds betweenthe contact pads on semiconductor devices and the lead fingers of leadframes are illustrated in U.S. Pat. Nos. 4,361,261, 4,527,730,4,600,138, 4,653,681, 4,765,531, and 5,465,899. However, such apparatusand methods do not address the problem of deformed lead frames and theireffect on the wire bonds.

[0009] Typically, the deformation of the lead frames and its effect onthe quality of wire bonds have been dealt with through the use of clampson portions of the lead frames during the wire bonding operation. InU.S. Pat. No. 4,434,347, a circular fixed clamp is used to retain thelead fingers of the lead frame during the wire bonding operation. Aspring loaded electrode is used to heat the end of the lead finger tohelp improve bonding of the wire.

[0010] In U.S. Pat. No. 5,322,207, a fixed clamp is used to retain thelead frame during the automated wire bonding process for connecting thebond pads of a semiconductor device to lead fingers of a lead frame.

[0011] In U.S. Pat. No. 5,307,978, a fixed clamp is illustrated for usein an apparatus and method for orienting bonding sites of a lead framehaving a plurality of bonding sites.

[0012] In U.S. Pat. No. 5,035,034, a hold-down clamp having amulti-fingered interchangeable insert for wire bonding semiconductorlead frames is illustrated. The clamp insert 21 includes a plurality ofindividual fingers 22 to be used to bias a lead finger of a lead framein the wire bonding process to provide a better wire bond.

[0013] In U.S. Pat. No. 3,685,137, jaws 26 and 28 of a lead frame clampare used to force the lead fingers of a lead frame into a fixed positionduring the wire bonding process.

[0014] In U.S. Pat. No. 4,821,945, a method and apparatus for the singlelead automated clamping and bonding of lead fingers of lead frames areillustrated. However, such apparatus and method are used to replace thefixed clamp during such wire bonding. Additionally, the individual clampis concentrically located with respect to the wire bonding apparatus andmust rotate therearound during wire bonding operations.

[0015] While such prior art apparatus and methods have been directed inattempting to solve the problems of forming reliable wire bonds betweenthe contact pads of semiconductor devices and lead fingers of leadframes, they have not been as successful as envisioned.

[0016] The present invention is directed to an improved wire bondingapparatus and method for forming such wire bonds.

SUMMARY OF THE INVENTION

[0017] The present invention is related to the apparatus and method offorming improved wire bonds between the contact pads on semiconductordevices and individual lead frame fingers of a lead frame. The presentinvention includes the use of an individual independent lead fingerclamp during the wire bonding process to provide increased stability ofthe individual lead finger for improved bonding. If desired, the presentinvention also provides for the use of a conventional fixed clamp forthe lead fingers during the wire bonding process in addition to theindividual independent lead finger clamp to provide increased stabilityof the individual lead finger for improved bonding. The presentinvention also contemplates the replacement of the fixed clamp withanother, or second, independent clamp in addition to the firstindividual independent lead finger clamp during the wire bondingprocess.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0018] The present invention will be better understood when thedescription of the invention is taken in conjunction with the drawingswherein:

[0019]FIG. 1 is a perspective view of the present invention used in awire bonding process.

[0020]FIG. 2 is a perspective view of a lead-over-chip semiconductordevice having the bond pads thereof connected to the lead fingers of alead frame.

[0021]FIG. 3 is a side view of the present invention used in the wirebonding of a semiconductor chip arrangement.

[0022]FIG. 4 is a perspective view of a second alternative type ofindependent lead clamp of the present invention.

[0023]FIG. 5 is a perspective view of a third alternative type ofindependent lead clamp of the present invention.

[0024]FIG. 6 is a perspective view of the use of two independent leadclamps of the present invention in a wire bonding operation with a leadfinger of a lead frame.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Referring to drawing FIG. 1, a semiconductor chip (die) 10 isshown being supported by the paddle 12 of a lead frame. A heat block 20is used to heat the paddle 12, die 10, and lead fingers 14 during thewire bonding process. As shown, a suitable wire 16 has one end thereof17 bonded to a bond pad of the die 10. The wire 16 may be of anysuitable type for connection and bonding purposes, such as gold, goldalloy, aluminum, aluminum alloy, etc. The other end 18 of the wire 16 isshown being bonded to the end 15 of a lead finger 14 of the lead frameby a suitable bonding apparatus 26. The bonding apparatus 26 may be ofany suitable type well known in the bonding area, such as a taillessthermosonic or ultrasonic capillary type bonding apparatus whichdispenses wire during the bonding process. As previously stated, thelead finger 14 is in contact with the heat block 20 to heat the leadfinger 14 to a suitable temperature for the bonding operation to helpinsure a satisfactory wire bond. If desired, in the wire bondingoperation, further shown in contact with lead finger 14 is a portion ofa conventional fixed clamp 22 used to clamp portions of the lead frameduring such bonding operations. The conventional fixed clamp 22 may beof any well known suitable type, such as those described hereinbefore,and is generic in shape. Further shown in drawing FIG. 1 isindependently actuated lead clamp 24 used in place of or in addition tothe conventional fixed clamp 22 to maintain the lead finger 14 inposition during the bonding process. The independent actuated lead clamp24 helps insure that the lead finger is in contact with the heat block20 during the bonding process and helps minimize any deflection of theend 15 of the lead finger 14 so that the bonding apparatus 26accurately, precisely contacts the end 15 to provide the desired wirebond. The action of independent actuated lead clamp 24, and if desiredthe additional use of fixed clamp 22, provides improved clamping of alead finger 14 during the wire bonding process as well as insures thatthe lead finger 14 is in intimate contact with the heat block 20 foreffectiveness.

[0026] During the wire bonding process, it is desirable for the heatblock to be heated to substantially 230 degrees Centigrade. Although theheat block may be any suitable temperature during the bonding operation,the heat block 20 temperature should not exceed 300 degrees Centigradeto prevent thermal damage to the die 10. It is further preferred thatthe bond of the end 18 of the wire 16 made to the end 15 of the leadfinger 14 be made at a temperature of substantially 190 degreesCentigrade for bonding effectiveness. It is also preferred that thebonding apparatus 26 exert a bonding force of substantially 50 to 100grams when bonding the end 18 of the wire 16 to the end 15 of leadfinger 14 for effective bond formation of the wire 16 to lead finger 14.

[0027] The independent actuated lead clamp 24 may be of any suitableshape for use in independently clamping the lead finger 14, in place ofthe use of conventional fixed clamp 22, such as square, semicircular,rectangular, arcuate, etc. Also, as shown, the independent actuated leadclamp 24 may be resiliently mounted through the use of a shoulder 50thereon abutting a spring 52 to control the amount of the force exertedon any lead finger 14 during the wire bonding operation. If desired, theindependent actuated lead clamp 24 may include insulation or cushioning25 on the end thereof. The independent actuated lead clamp 24 isactuated independently of bonding apparatus 26 and has the capability ofindependent movement along the x-axis, y-axis and z-axis with respect tothe bonding apparatus 26. The independent actuated lead clamp 24 is alsofree to move about the bonding apparatus 26 and the central axis of thedie 10 so that any lead finger 14 that is to be connected to bond padson the die 10, regardless of location, may be accommodated. Theindependent actuated lead clamp 24 does not need to be, and preferablyis not, concentrically centered about the bonding apparatus 26 so thatit will not interfere with the operation thereof. Any desired number ofindependent actuated lead clamps 24 may be used about the bondingapparatus 26 to minimize the amount of movement of the independentactuated lead clamp 24 between wire bonding operations. The independentactuated lead clamps 24 may be located in quadrants about the die 10, orin any manner as desired.

[0028] Referring to drawing FIG. 2, a lead over chip configuration usingthe present invention is shown. The lead fingers 14 are located over thechip (die) 10 for wire bonding thereto. In such a configuration, thelead fingers 14 are secured to the die 10 by insulating adhesive strips30. During the bond operation, one or more of the independent actuatedlead clamp 24 clamps the end 15 of lead finger 14 prior to the bondingof a wire 16 thereto by one or more of the bonding apparatus 26. Theindependent actuated lead clamp 24 applies sufficient pressure to theend 15 of the lead finger 14 to compress the insulating adhesive strips30 to insure a satisfactory bond between the end of any wire 16 and theend 15 of the lead finger 14.

[0029] Referring to drawing FIG. 3, a die 10 is shown having a pluralityof wires 16 bonded thereto. As shown, one or more of the independentactuated lead clamps 24 contacts the end 15 of lead finger 14 aft of thearea of the wire end 18 to the lead finger 14. The bonds of the wire end18 to the end 15 of the lead finger 14 are typically a wedge type wirebond, although a ball bond may be made if desired. As shown, the heatblock 20 is in contact with the paddle 12 of the lead frame and the leadfingers 14.

[0030] Referring to drawing FIG. 4, a portion of a lead finger 14 isshown in conjunction with a bonding apparatus 26 and modifiedindependent lead clamp 22′. The independent lead clamp 22′ is formedhaving a modified end or foot 23 thereon to provide a larger clampingarea of the independent lead clamp 22′ on the end 15 of the lead finger14 during bonding operations. The modified end or foot 23 issubstantially the same width as the lead finger 14 and may be mounted tohave articulated movement about the end of the independent lead clamp22′, such as using a pin 125 extending through suitable apertures in apair of ears 27 attached to the foot 23 and the end of the modifiedindependent lead clamp 22′ for illustration purposes.

[0031] Referring to drawing FIG. 5, an independent conventional fixedclamp 22′ is shown having a modified end or foot 23′ located on the endthereof. The end or foot 23′ may be integrally attached to theconventional fixed clamp 22′ or may have an articulated mountingarrangement, such as shown in drawing FIG. 4. In this instance, themodified end or foot 23′ is generally semicircular, or arcuate, inconfiguration so as to engage a large portion of the end 15 of the leadfinger 14 surrounding the bonding apparatus 26 during the wire bondingoperation to hold the end 15 in position.

[0032] Referring to drawing FIG. 6, the independent actuated lead clamp24 is shown in relation to the bonding apparatus 26 on the end 15 of alead finger 14 as well as further being shown in relation to a secondindependently actuated clamp 150 located thereon during wire bondingoperations. The second independently actuated clamp 150 may be of anysuitable type and structure such as described and illustratedhereinbefore. The actuated lead clamp 24 and second independentlyactuated clamp 150 may be actuated independently of each other andindependently of the bonding apparatus 26 as described and illustratedhereinbefore.

Method of Bonding

[0033] Referring to drawing FIGS. 1 through 3, in the method of thepresent invention, a die 10 is positioned within the bonding area of thebonding apparatus 26. If desired, for use in addition to an individualindependent actuated lead clamp 24, a conventional fixed clamp 22 servesto help straighten the lead frame and position the lead fingers 14during subsequent bonding operations. Next, the die 10 and the leadfinger 14 are heated to the desired temperature before bondingoperations by the heat block 20. At this time, the independent actuatedlead clamp 24 is engaged, moved to the appropriate lead finger 14 whichis to have a wire bonded thereto, and the actuated lead clamp 24actuated to clamp the end 15 of the lead finger 14 against the heatblock 20 or the insulating adhesive strip 30. The wire bonding apparatus26 is then actuated to form a wire bond on end 17 of wire 16 to anappropriate bond pad on die 10. After the formation of the bond of end17 of wire 16 to the bond pad of die 10, the bonding apparatus is movedto appropriate end 15 of lead finger 14 for the formation of a suitablewire bond thereto by end 18 of wire 16. After the formation of the bondof the end 18 of wire 16 to the end 15 of lead finger 14, theindependent actuated lead clamp 24 and the bonding apparatus 26 areactuated to substantially simultaneously remove the independentlyactuated lead clamp 24 and the bonding apparatus 26 from the end 15 ofthe lead finger 14. Alternately, the bonding apparatus 26 is actuated toremove the apparatus from the bond location at the end 15 of the leadfinger 14 either prior to or after the removal of the independentactuated lead clamp 24 from a lead finger 14. During the removal of thebonding apparatus 26 from the end 15 of the lead finger 14, if used inaddition to the independent actuated lead clamp 24, a conventional fixedclamp 22, if in contact with a lead finger 14, supplies the necessaryforce to retain the finger 14 in position relative to other lead fingerslocated around die 10, both bonded and unbonded. As previously stated,it is not necessary for the independent actuated lead clamp 24 to remainin contact with the end 15 of lead finger 14 during the removal of thebonding apparatus 26 therefrom. After the wire 16 has been bonded to thedesired bond pad of die 10 and end 15 of lead finger 14, the process isrepeated until all desired wire bonds between lead fingers 14 and bondpads of die 10 are completed.

[0034] If desired to have additional clamping of the lead finger 14,either a fixed clamp 22 and/or a second independent actuated lead clamp24 may be used with the bonding apparatus 26. The second independentactuated lead clamp 24 may be actuated and moved from the lead finger 14with, before or after the removal of the bonding apparatus 26 from thelead finger 14.

[0035] It will be understood that the present invention may havechanges, additions, deletions, modifications, and sequence of operationwhich fall within the scope of the invention. For instance, the fixedclamp may be eliminated and a second independent actuated lead clampused in its place.

What is claimed is:
 1. Apparatus for bonding a wire to a bond padlocated on a semiconductor chip and a lead finger of a lead frame, saidapparatus comprising: bonding apparatus having a portion thereof fordispensing of said wire to be bonded to said bond pad and said leadfinger and bonding said wire to said bond pad or said lead finger; anindependent clamp for engaging another portion of said lead fingerbefore said bonding of said wire thereto, said independent clamp beingmovable; and a conventional fixed clamp for engaging a portion of saidlead finger adjacent said independent clamp.
 2. The apparatus of claim1, wherein said independent clamp is located between said bondingapparatus and said conventional fixed clamp engaging said portion ofsaid lead finger during said bonding of said wire thereto.
 3. Theapparatus of claim 1, wherein said independent clamp includes having anability to move independently in an x-axis, y-axis and z-axis.
 4. Theapparatus of claim 1, wherein said independent clamp is movableindependently in any direction of a movement of said bonding apparatus.5. The apparatus of claim 1, wherein said apparatus further comprises:heating apparatus located beneath said semiconductor chip.
 6. Theapparatus of claim 1, wherein said apparatus further comprises: heatingapparatus located beneath said lead finger.
 7. The apparatus of claim 6,wherein said semiconductor chip is heated before said wire is bondedthereto.
 8. The apparatus of claim 1, wherein said independent clamp isresiliently mounted.
 9. The apparatus of claim 8, wherein saidindependent clamp is resiliently mounted through use of a springengaging a portion of said independent clamp.
 10. The apparatus of claim1, wherein said independent clamp has an end portion thereof which isinsulated.
 11. The apparatus of claim 1, wherein said independent clamphas an end portion thereof which is semicircular in shape.
 12. Theapparatus of claim 1, wherein said independent clamp has an end portionthereof which is arcuate in shape.
 13. The apparatus of claim 1, whereinsaid independent clamp has an end portion thereof which is articulatedfor movement.
 14. The apparatus of claim 1, wherein said independentclamp is located between said bonding apparatus and said conventionalfixed clamp engaging said portion of said lead finger during saidbonding of said wire thereto.
 15. Apparatus for bonding a wire to a bondpad located on a semiconductor chip and a lead finger of a lead frame,said apparatus comprising: bonding apparatus having a portion thereoffor dispensing of said wire to be bonded to said bond pad and said leadfinger and bonding said wire to said bond pad or said lead finger; aconventional fixed clamp for engaging a portion of said lead finger; andan independent clamp for engaging another portion of said lead fingerbefore said bonding of said wire thereto, said independent clamp beingmovable, said independent clamp including having an ability to move asdesired in an x-axis direction, a y-axis direction, and a z-axisdirection concurrently.
 16. The apparatus of claim 15, wherein saidindependent clamp is movable independent of a movement of said bondingapparatus.
 17. The apparatus of claim 15, wherein said apparatus furthercomprises: heating apparatus located beneath said semiconductor chip.18. The apparatus of claim 17, wherein said apparatus further comprises:heating apparatus located beneath said lead finger.
 19. The apparatus ofclaim 17, wherein said semiconductor chip is heated before said wire isbonded thereto.
 20. The apparatus of claim 15, wherein said independentclamp is resiliently mounted.
 21. The apparatus of claim 20, whereinsaid independent clamp is resiliently mounted through use of a springengaging a portion of said independent clamp.
 22. Apparatus for bondinga wire to a bond pad located on a semiconductor chip and a lead fingerof a lead frame, said apparatus comprising: bonding apparatus having aportion thereof for dispensing of said wire to be bonded to said bondpad and said lead finger and bonding said wire to said bond pad or saidlead finger; a first independent clamp for engaging a portion of saidlead finger, said first independent clamp located adjacent said bondingapparatus engaging said portion of said lead finger during said bondingof said wire thereto; and a second independent clamp for engaginganother portion of said lead finger before said bonding of said wirethereto.
 23. The apparatus of claim 22, wherein said first independentclamp includes having an ability to move as desired in an x-axisdirection, a y-axis direction, and a z-axis direction concurrently. 24.The apparatus of claim 22, wherein the first independent clamp ismovable independent of a movement of said bonding apparatus.
 25. Theapparatus of claim 22, wherein said apparatus further comprises: heatingapparatus located beneath said semiconductor chip.
 26. The apparatus ofclaim 25, wherein said apparatus further comprises: heating apparatuslocated beneath said lead finger.
 27. The apparatus of claim 25, whereinsaid semiconductor chip is heated before said wire is bonded thereto.28. The apparatus of claim 25, wherein said first independent clamp isresiliently mounted.
 29. The apparatus of claim 28, wherein said firstindependent clamp is resiliently mounted through a use of a springengaging a portion of said independent clamp.
 30. The apparatus of claim23, wherein said second independent clamp is located adjacent saidbonding apparatus and said first independent clamp engaging said portionof said lead finger during said bonding of said wire thereto.
 31. Theapparatus of claim 23, wherein said second independent clamp includeshaving said ability to move as desired in an x-axis direction, a y-axisdirection, and a z-axis direction.
 32. The apparatus of claim 23,wherein said second independent clamp is movable independent of saidmovement of said bonding apparatus.
 33. The apparatus of claim 23,wherein said first independent clamp is movable independent of amovement of said bonding apparatus and said second independent clamp.